The last time Ford rolled a Mustang Mach 1 off the assembly line was way back in 2004, and the next time will be in 2021. It will amount to a 17-year hiatus when the limited edition Mach 1 makes its return next year, and this time it will be touting a 5.0-liter V8 engine with 480 horsepower at 7,000 rpm, and 420 lb.-ft. of torque at 4,600